Reply To: CG Dra: a VSS campaign

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Maxim Usatov

Eclipses No(s): 61, 62
State: Quiescence

CG Dra can be very deceptive. Look at how different eclipse profiles are, separated by just 4 hours. Poor quality data, combined with flickering due to the bright spot on the accretion disk of the white dwarf makes the second eclipse appear almost symmetrical and much deeper than the first one. Wild flickering creates bumps in the orbital hump, sometimes right before the ingress (2nd eclipse). Random patterns due to the measurement uncertainty at the eclipse minimum (1st eclipse), then, removes or adds depth, and flickering at the egress (2nd eclipse) may occasionally play another joke. I think this is what is happening here. Two asymmetric eclipses with normal ~ 0.1 mag orbital hump (U/N/A), distorted by uncertainty and flickering, so they appear to be different.

A question: should I continue assigning eclipse types just as they appear on the light curve, like I did before, or should I compensate for these distortions due to poor quality data? There is more value in compensating, but if I do this, I’ll need to reclassify all poor-quality eclipses I’ve filed earlier (Whew…)

It would also be interesting to correlate FWHM with sigma. The night was pretty clear and dark. There was no extreme in temperatures. Why photometry quality suffered – I don’t know.